Ichiro is a highly imaginative, but lonely, boy growing up in urban Tokyo. Every day he comes home to the empty apartment he shares with his railroad worker father and his restaurant hostess mother. His only friends are a toy maker name Shinpei Inami and a little girl named Sachicko. The only other kids that are around is a gang of kids led by a bully named Gabara. To escape his loneliness, Ichiro imagines that he is on Monster Island where he befriends Minya, the son of Godzilla. It is through his daydreams that he watches Godzilla and Minya fight other monsters, including one also named Gabara who is just as bad a bully as the one that is tormenting Ichiro. It is through these daydreams that he learns that it is okay to fight back and face his fears. These lessons also help him to outwit a couple of bumbling bank robbers as well as finally have the guts to stand up to Gabara and his gang.

Minya: Godzilla says that I should learn to fight my own battles, y'know. Ichiro Miki: Against big guys? Minya: Uh-huh.

Minya: How do you like that, weirdo!

Movie Trivia:

Eiji Tsuburaya was bedridden during production, so Ishir˘ Honda took over the effects direction, which resulted in limited special effects work and stock footage. Tsuburaya did not work on the film at all, aside from the stock footage, but is credited out of respect.

This was deliberately set out be a Godzilla film aimed at small children for release during the Christmas season. Among the more unusual aspects of the film was the casting of Eisei Amamoto as a toy designer and friend to the little boy. Amamoto was normally cast in other films as the slimiest of criminals, gangsters and henchmen.

This was the final appearance of the Gorosaurus. Manda, Kamakiras, Kumonga and Minya would not be seen again until Godzilla: Final Wars.

The "Monster March" theme song from the Japanese version is composed by Genta Kano, best known for composing the theme song to the Japanese classic, T˘ky˘ nagaremono (1966).

This was Yoshifumi Tajima's final appearance in a Showa Era film. His next, and final, series appearance was in the first film of the Hessei era, Gojira (1984).